Turbulence generating yarn feed needle

Abstract

An improved fluid jet bulking device is disclosed in which a yarn feed needle is eccentrically positioned with respect to a venturi and is further provided with a staged means for generation of turbulence in the yarn bulking fluid. The needle may include a flanged end portion which develops a first stage of turbulence generation in the fluid within the venturi inlet, an accelerated flow passage. A second stage of turbulence generation at the distal end of the yarn feed needle augments the level and intensity of turbulence generated in the compressible fluid passing through the device. Fluid flow in the venturi inlet is non-axisymmetric due to the eccentricity so that the successive stages of turbulence generation interact with one another to develop a highly complex turbulent flow regime. The yarn feed needle is preferably constructed such that the turbulent flow generated by the successive stages induces a lateral vibration to the distal end of the needle, thereby creating a non-steady three-dimensional flow. As an alternative to the flanged end porton, a plurality of generally radially extending spokes may be provided at the distal end of the needle to effect a first stage of turbulence generation. In another alternative, a conical surface of the distal end may be provided with suitable scoring marks to further develop turbulent flow in a compressible fluid passing between the yarn feed needle and the venturi.

What is claimed is: 
     
       1. In yarn bulking apparatus having a housing with a central axis, an internal cavity, a venturi eccentrically positioned relative to the axis at one end of the housing, a yarn feed opening in a second end of the housing, and means for supplying a pressurized compressible fluid to the internal cavity upstream of the venturi inlet, an improved device for generating turbulence in the venturi inlet comprising: first means for generating turbulence in the compressible fluid, positioned in the venturi inlet providing a first stage of turbulence generation;   second means for generating turbulence in the compressible fluid, positioned in the venturi inlet downstream of the first means, providing a second stage of turbulence generation; and   yarn feed needle cantilevered from an upstream end of the internal cavity, extending coaxially through the internal cavity to the venturi inlet, having a yarn feed passage communicating with the yarn feed opening and extending through the yarn feed needle, the second means for generating turbulence being at a distal end of the yarn feed needle and the first means for generating turbulence being upstream of the distal end.   
     
     
       2. The apparatus of claim 1, wherein the yarn feed needle includes a generally cylindrical shank portion with the yarn feed passage coaxially disposed therethrough, the shank portion having a sufficiently thin wall thickness that turbulence induced by the first and second turbulence generating means at the distal end induces lateral vibration of the distal end. 
     
     
       3. The apparatus of claim 2, wherein the yarn feed needle has a ratio of cantilevered length to needle diameter which permits the distal end to vibrate in response to the turbulence with an amplitude that is less than the minimum radial clearance between the distal end and the venturi inlet. 
     
     
       4. The apparatus of claim 1, wherein the first means for generating turbulence includes a generally circular disc at the distal end, having a frustoconical peripheral surface, the peripheral surface defining an acute angle along its common edge with the upstream face of the disc. 
     
     
       5. The apparatus of claim 4, wherein the frustoconical surface has a cone angle corresponding to the cone angle of the venturi inlet so as to provide radial clearance around the disc which is essentially variant in the axial direction. 
     
     
       6. The apparatus of claim 1, wherein the first means for generating turbulence includes a plurality of outwardly extending spokes which induce turbulent eddies in gas passing between the yarn feed needle and the venturi inlet. 
     
     
       7. The apparatus of claim 6, wherein each spoke extends radially outwardly from the yarn feed needle and the plurality of spokes are substantially equiangularly spaced. 
     
     
       8. The apparatus of claim 1, wherein the first means for generating turbulence includes a roughened peripheral surface at the distal end of the yarn feed needle. 
     
     
       9. The apparatus of claim 8, wherein the roughened surface includes a plurality of scored grooves. 
     
     
       10. The apparatus of claim 1, wherein the second means for generating turbulence includes an abrupt flow area enlargement at the distal end of the yarn feed needle. 
     
     
       11. A method of bulking a multi-filament yarn comprising the steps of: supplying a multi-filament yarn to a yarn feed needle of a bulking device;   supplying a flow of compressible fluid to a fluid channel extending through the bulking device, the channel having a generally annular portion surrounding the yarn feed needle;   accelerating the compressible fluid by directing the fluid as an annular flow into an eccentrically positioned venturi inlet;   abruptly contracting the annular flow portion within the venturi inlet to generate turbulence and a three-dimensional flow field;   abruptly enlarging the annular flow portion to a generally cylindrical flow regime at the downstream end of the yarn feed needle to further increase the turbulence level in the fluid;   passing the multifilament yarn into the turbulent compressible fluid so as to texturize the yarn; and   passing the texturized yarn and the turbulent fluid through a venturi throat.   
     
     
       12. The method of claim 11, including the further step of: expanding the fluid in the venturi exit so as to decrease fluid velocity and reduce tension exerted by the fluid on the yarn.   
     
     
       13. The method of claim 11, wherein the steps of abruptly enlarging and abruptly decreasing generate turbulence having sufficient intensity to vibrate the yarn feed needle within the venturi inlet and thereby induce an unsteady flow field therearound.